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What are the intercostal muscles?
- 3 intercostal muscles
- 1) external intercostal
- 2) internal intercostal
- 3) innermost intercostal
What are the characteristics of the external intercostal? Attachment, fiber direction, function, & nerve supply.
- Attachment: lower borders of ribs 1-11 to upper borders of ribs 2-12
- Fibers: run down and forward at the costochondral joint, replaced by external intercostal membrane
- Function: elevate rib cage, inspiration
- Nerve: corresponding intercostal nerves
What are the characteristics of the internal intercostal?
- attachment: lower margins of ribs, costal cartilages and grooves (same as external).
- fibers: run down and backward, the intercostal membrane is near the vertebrae.
- function: muscle of experation
- nerve: corresponding intercostal nerves
What are the characteristics of the innermost intercostal muscle?
- It has 3 parts
- 1) innermost intercostal muscle fibers: few fibers between the ribs; mostly membrane.
- 2) subcostalis muscle: found at angle of rib only. attachment: between ribs posteriorly and may cross 1 or 2 ribs and attach to the 3rd rib. function: expiration.
- 3) sternocostalis muscle (transversus thoracis): found near sternum only. attachment: back of xiphoid process and sternum, inserts in the costal cartilages. nerve: interostal nerves. function: expiration
fibers: run down and backward
Where is the posterior intercostal neurovascular bundle located?
between internal intercostal muscles and the innermost interostal muscles.
Where is the subcostal space located?
space below the 12th rib
How many intercostal spaces are there?
Where is the nipple of the breast located?
Intercostal space 4
Arterial blood supply of the thoracic cage (4)
- 1: Internal thoracic artery branched from subclavian artery.
- 2: highest intercostal artery branched from costocervical
- 3: posterior intercostal artery branched directly from thoracic aorta
- 4: subcostal artery branched directly from thoracic aiorta
What supplies the arterial anterior aspect of the intercostal spaces?
Internal thoracic artery branched from subclavian artery.
What supplies the arterial posterior aspect of the intercostal spaces? Differentiate between spaces 1, 2-11, and 12
- 1: highest intercostal artery
- 2-11: posterior intercostal arteries
- 12: subcostal artery
Venous blood supply of the thoracic cage: Anterior aspect
internal thoracic vein drains into the braciocephalic vein
venous blood supply of the thoracic cage: posterior aspect
supplied by the azygous system
what veins supply the posterior right side of the thoracic cage?
- 1 intercostal space: highest intercostal vein drains into the brachiocephalic vein.
- 2 and 3 intercostal space: joins higher intercostal , drains into azygos
- 4-11 intercostal space: intercostal veins drain directly into the azygous vein.
- 12 intercostal space: subcostal vein drains directly into azygous vein.
Where does the azygous vein drain?
into the superior vena cava
what veins supply the posterior left side of the thoracic cage?
- 1 intercostal space: highest intercostal vein drains into brachiocephalic vein
- 2-4 intercostal space: intercostal veins join to give accessory hemiazygous vein.
- 5-11 intercostal space: intercostal veins and the subcostal vein (12th vein) join together to give the hemiazygous vein.
What 2 paths can the accessory hemiazygous and hemiazygous veins take to drain?
- 1: they cross to right side independantly and drain into azygous vein
- 2: they join as a single unit and drain into azygous vein
Where else may the accessory hemiazygous vein drain?
into the brachiocephalic vein
how many layers of penetration are in the mid-axillary line?
what are the layers of penetration?
- 1: skin
- 2: superficial fascia
- 3: deep fascia
- 4: serratus anterior
- 5: external intercostal muscle
- 6: internal intercostal muscle
- 7: innermost intercostal muscle
- 8: endothoracic fascia
- 9: parietal pleura
- 10: pleural cavity
- 11: visceral pleura
- 12: lungs
What is the function of the endothoracic fascia?
prevent parietal pleura which surrounds the lungs from rubbing against the innermost intercostal muscles.
What is thickening of the endothoracic fascia called?
thickening over the apex of the lung aka sibson's fascia
Spaces of the thoracic cavity
- 1: 2 pleural cavities that are separate enclosed spaces from one another with pleural fluid.
- 2: mediastinum
what are the structures inside the thoracic cavity
- 2: lungs
- 3: trachea
- 4: esophagus
- 5: vagus and phrenic nerves
what are the pleural reflections?
- 1: pleural cavity
- 2: pleaural fluid
- 3: pleural membranes
- 4: removal of fluid
- 5: parietal pleura
- 6: visceral pleura
- 7: cupola
what is the pleural cavity?
enclosed space that includes fluid
what is the function of pleural fluid?
minimize friction between parietal pleura and visceral pleura
pleural membranes do not cover?
root of the lung
how to remove pleura fluid?
with mid-axillary tap
where is the parietal pleura?
lines the muscle wall
where is the visceral pleura?
what is the cupola and where is it?
area of parietal pleura, it is located on the apex of the lung in the thoracic inlet
what are the pleural recesses?
- 1: costo diaphragmatic recess
- 2: costo mediastinal recess
- 3: costo vertebral recess
where is the costo diaphragmatic recess?
junction of costal and diaphragmatic parietal pleura near mid axillary line.
pleural cavity tap can be done here in intercostal space 9
What is the function of recesses?
allow expansion of lung during inspiration
what arteries supply the parietal pleura?
intercostal and internal thoracic arteries
what artery supplies the visceral pleura?
bronchial artery which supplies the lung
what nerves supply the parietal pleura?
intercostal nerves T1-T11 subcostal and phrenic nerve (Cn 3,4,5)
function of the phrenic nerve?
motor nerve to the diaphragm
what nerves supply the visceral pleura?
none. insensitive to pain, no sensory innervation
Where is the mediastinum located?
medial region between the 2 pleural cavities.
what does the mediastinum contain?
all structures in chest except lungs and pleural sacs
what is the sternal angle of the mediastinum?
T4 level. line through sternal angle divides mediastinum into superior and inferior sections.
what does the superior mediastinum contain?
arch of aorta and branches
what are the branches of the aorta of the superior mediastinum?
- 1: brachiocephalic trunk
- 2: left common carotid artery
- 3: left subclavian vein
- 4: brachiocephalic vein
- 5: superior vena cava
- 6: thymus (children only)
- 7: esophagus
- 8: trachea
- 9: thoracic duct
how is the brachiocephalic vein formed in the mediastinum?
joining of subclavian vein and internal jugular vein
how is the superior vena cava formed?
joining right and left brachiocephalic veins
what are the compartments of the inferior mediastinum?
- 1: anterior mediastinum
- 2: middle mediastinum
- 3: posterior mediastinum
location of the anterior mediastinum?
posterior surface of the sternum to anterior surface of pericardial sac
what is the anterior mediastinum made up of?
- 1: fatty tissue
- 2: thymus (infants)
- 3: lymph nodes
what is the middle mediastinum made up of?
- 1: heart
- 2: pericardium
- 3: main bronchi
- 4: great vessels
where is the posterior mediastinum located?
posterior to pericardial sac and diaphragm and anterior to thoracic vertebrae 5-12
what is the posterior mediastinum made up of?
- 1: esophagus
- 2: thoracic aorta
- 3: azygos system
- 4: thoracic duct
- 5: vagus nerve
- 6: splanchnics nerves from sympathetic chain
what structure is not in the posterior mediastinum?
what does a mediastinoscopy involve?
removal of tissue from anterior and superior mediastinum to examine the lymph nodes. The inciscion is made at the jugular notch.
physical characteristics of the trachea
- 15-20 "C" bars of cartilage
- 9-15 cm long and 2.5 cm in diameter
- begins at the neck at cv 6
- biforcates at sternal angle (tv 4) into right and left main bronchi
what are structures anterior to trachea?
- arch of aorta
- origins of brachiocephalic and left common carotid arteries
what are structures posterior to trachea?
- esophagus: right side= azygos vein and right vagus nerve
- esophagus: left side = arch of aorta, left common carotid, left subclavian artery, left vagus nerve
what does trachea do just before it biforcates?
at the sternal angle, it deviates towards the right because of the heart.
branches of the trachea
- right main bronchus: wider and shorter it is more vertical than the left. gives off superior lobar bronchus before entering the hilum then divides further into middle and inferior lobar bronchi.
- left main bronchus: narrower and longer it is more horizontal than the right. passes interior to the esophagus. divides in the hilum intol superior and inferior lobar bronchii
what arteries supply the trachea?
- superior thyroid artery
- inferior thyroid artery
- bronchial arteries
- internal thoracic artery
what nerves supply the trachea?
what are the anatomical features of the lungs?
what surfaces make up the base of the lung?